Parents need to know that the movie, short on plot, soon seems like a prolonged jump scene: characters crawl, trudge, and fight their way through dark tunnels, some filled with skulls. The monsters are initially unreadable shapes that eventually show themselves as flying-swimming-spelunking creatures. Violence can be graphic, including bloody penetrations, explosions, and draggings. Characters avoid cursing outright, but do call each other names ("jackass," for example). The film includes tense scenes -- creatures lurking in the dark, close quarters and characters screaming -- that might trouble younger viewers.

Families can talk about the characters' choices. (As they are largely undistinguishable, their choices seem functions of the group, even when they're arguing.) Some act out of ambition, others fear or anger, but all make typically bad horror-action movie choices: they go off on their own, distrust one another, head directly to the darkest corner of the screen space. How do their actions create tension? Do they have alternative choices?

The good stuff

Messages: Monsters are mean, some ambition and competition at the start; survivors pull together by end.

What to watch for

Violence: Monsters attack, bloody bodies left in their wake, some explosions.

Sex: Very brief flirting, a man cuts open a woman's wet suit to give her mouth to mouth, a woman climber wears shorts and a sports bra.

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